Mercedes Sosa, the Argentine singer known as one of the leaders of the "nueva cancion" movement and whose songs became synonymous with social change for generations of Latin Americans, has died in Buenos Aires, aged 74.

The cause of her Oct. 4 death was given as kidney failure. The singer, who had continued to record and perform right up until until her death, released over 70 albums in her lifetime and had recently garnered attention thanks to a pair of 2009 Sony albums -- "Cantora 1" and "Cantora 2" -- which featured her singing many of her hits as duets with various guest singers. "Cantora 1" was nominated for a Latin Grammy in the album of the year category.

Sosa was defined as much for her powerful contralto as for being a proponent of Argentine folklore and for championing social causes through her music and beyond. Her role in this regard was particularly apparent during the military dictatorship in Argentina (1976-1983), which led to her living in exile in Europe. Sosa left Argentina at the end of the 1970s and returned in 1982 for a dozen legendary concerts in Buenos Aires' Teatro Colón.

Although not a songwriter, Sosa became a central figure in the development of the "nueva cancion" movement that swept Latin America in the 1970s as a seminal interpreter of works of other prominent and social-minded singer/songwriters, such as Silvio Rodriguez, Atahualpa Yupanqui, Pablo Milanes, David Lebon, Piero, Milton Nascimento, Raimundo Fagner, León Gieco, Violeta Parra and Víctor Heredia.

At a time when military dictatorships raged throughout Latin America, Sosa became one of the proponents of a more left-leaning musical movement whose songs dwelt on social justice and rebellion against oppression. Beyond her influence on social issues, however, her renditions of songs like Parra's "Gracias a la Vida" and Maria Elena Walsh's "Como La Cigarra" became hymns for literally generations of Latin Americans until this day. She also won Latin Grammy awards in 2000, 2003 and 2006.

Born Haydee Mercedes Sosa on July 9, 1935 in San Miguel de Tucumán, a rural area in Norhwestern Argentina, Sosa was of mixed Indian and French ancestry and was affectionately nicknamed "La Negra" (The Dark One) for her dark countenance. She began singing folklore as a child and gained her first recognition when she won her a radio talent contest at the age of 15.

Sosa has been lying in state in Buenos Aires' National Congress building, where thousands of fans have been coming to pay their respects at her open coffin before her cremation, expected to take place this afternoon (Oct. 5)